Trolley mounted hoists, overhead monorail carrier systems, and other similar conveyor apparatuses are frequently used in manufacturing plants, factory buildings, and other industrial operations to movably support instruments, tools, various materials, pre-assembled components, and a variety of other payloads. For example, in the automotive industry, overhead monorail carrier systems are used to repositionably support a wide range of tools (e.g., hoists, torque tubes, fastening equipment, etc.) at predetermined locations along engine, transmission, and vehicle assembly lines.
A typical overhead monorail carrier system will include a number of trolley devices (often referred to as a carrier or carriage), each extending downward from a corresponding overhead transfer bridge or rail. The bridge or rail system may be supported from an erected tubular column system, or from the ceiling, roof, or trusses of the building between adjacent rows of structural columns which support the roof or trusses. The transfer bridges are arranged in parallel along the assembly line, and spaced apart from one another. The floor space between the individual transfer bridges defines a number of work areas or storage spaces.
Each trolley is repositionable—i.e., slides or is slidable, from end-to-end along the transfer bridge, between adjacent rows of structural columns. The trolley normally comprises one or more wheels rotatably mounted to high-strength supporting plates (e.g., cast hardened or hardened alloy steel) by a complementary bearing. The wheels of the trolley roll along a transverse track, generally defined along the length of a cavity inside a hollow rail, or the inner flange surfaces of an I-beam bridge.
The hoists and equipment that is attached to the under hung bridges can unintentionally sway when the trolley is shifted from side-to-side. This may cause the trolley to inadvertently drift into the operator's way if not properly restrained. The most common way to restrain the trolley is via pneumatic or mechanical latching mechanisms, or by strapping the equipment to the nearest column by one or more bungee cords.